A slab casting method

Abstract

The application relates to a slab casting method, in particular to a slab casting method. The method comprises the following steps: placing a double-flow occupying device at the bottom of a submerged nozzle to obtain a nozzle with a double-flow occupying device; baking the nozzle with the double-flow occupying device; installing the baked nozzle with the double-flow occupying device at the lower part of a tundish to carry out casting; wherein the flow of argon blowing of the upper nozzle is controlled in stages during the casting process. The application solves the technical problem that the existing technology for preventing the crystallizer from splashing is relatively complex and the crystallizer flow field is not comprehensively considered. The method can effectively reduce the splashing amount by 10-30% during the casting process.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of continuous casting, in particular to a slab casting method. BACKGROUND

[0002] Slab continuous casting is an important way to improve the output of steel, and the casting process is an important part of continuous casting. In addition to the secondary oxidation of molten steel and the rolling of slag, spatter is also an important factor affecting the stability of the casting process.

[0003] In the casting process, the molten steel hits the bottom of the submerged nozzle, bounces out and spouts from the submerged nozzle in a jet shape. Since there is no molten steel in the crystallizer at the time of casting, the jetted molten steel flow will have the following hazards: (1) splashing into the corner gap of the crystallizer to form cold steel, affecting product quality; (2) burning out the gas blowing and liquid level fluctuation control system, causing significant economic losses; (3) endangering the personal safety of the operator.

[0004] Currently, the existing technology mainly adds corresponding devices in the crystallizer, which is relatively complex. The existing technology does not simultaneously consider the technical scheme of the crystallizer flow field and molten steel spatter. SUMMARY

[0005] The present application provides a slab casting method to solve the technical problem that the existing anti-crystallizer spatter technology is relatively complex and does not comprehensively consider the crystallizer flow field.

[0006] In a first aspect, the present application provides a slab casting method, which comprises:

[0007] Placing a double-flow placeholder at the bottom of the submerged nozzle to obtain a nozzle with a double-flow placeholder;

[0008] Baking the nozzle with the double-flow placeholder;

[0009] Installing the baked nozzle with the double-flow placeholder at the lower part of the tundish for casting; wherein the flow of argon gas blowing from the upper nozzle is controlled in stages during the casting process.

[0010] Optionally, the double-flow placeholder is composed of a closed triangular prism steel support with a handle, and the cross section of the double-flow placeholder is an isosceles triangle; wherein,

[0011] The size parameters of the double-flow placeholder are designed according to the size parameters of the submerged nozzle.

[0012] Optionally, the design of the size parameters of the double-flow placeholder according to the size parameters of the submerged nozzle comprises:

[0013] The height of the double strand flow placeholder satisfies the following relationship with the outlet width of the submerged nozzle:

[0014] h = W - (2-4)

[0015] In the formula, h represents the height of the double strand flow placeholder, and W represents the outlet width of the submerged nozzle.

[0016] Optionally, the size parameters of the double strand flow placeholder are designed according to the size parameters of the submerged nozzle, including:

[0017] The length of the bottom side of the double strand flow placeholder satisfies the following relationship with the inner diameter of the submerged nozzle:

[0018] a = D + (2-4)

[0019] In the formula, a represents the length of the bottom side of the double strand flow placeholder, and D represents the inner diameter of the submerged nozzle.

[0020] Optionally, the size parameters of the double strand flow placeholder are designed according to the size

[0021] parameters of the submerged nozzle, including:

[0022] The bottom angle of the double strand flow placeholder is equal to the inclination angle of the submerged nozzle.

[0023] Optionally, the flow of argon gas blown by the upper nozzle is controlled in stages, including:

[0024] The flow of argon gas blown by the upper nozzle is controlled according to the relationship between the casting speed and the melting of the double strand flow placeholder.

[0025] Optionally, the flow of argon gas blown by the upper nozzle is controlled according to the relationship between the casting speed and the melting of the double strand flow placeholder, including:

[0026] When the casting speed increases from 0 to before the placeholder melts, the gas blowing amount of the upper nozzle is controlled to be 0.5-2 L / min.

[0027] Optionally, the flow of argon gas blown by the upper nozzle is controlled according to the relationship between the casting speed and the melting of the double strand flow placeholder, including:

[0028] When the placeholder melts to the casting speed of 0.8 m / min, the gas blowing amount of the upper nozzle is controlled to be 2-4 L / min.

[0029] Optionally, the flow of argon gas blown by the upper nozzle is controlled according to the relationship between the casting speed and the melting of the double strand flow placeholder, including:

[0030] When the casting speed increases from 0.8 m / min to the target casting speed, the gas blowing amount of the upper nozzle is controlled to be 3-10 L / min.

[0031] Optionally, the baking time is 1-2h.

[0032] The above technical solution provided by the embodiments of the present application has the following advantages compared with the prior art:

[0033] The slab casting method provided by the embodiments of the present application adds a double-flow placeholder on the basis of not changing the original submerged entry nozzle structure, and cooperates with the change of the blowing flow, eliminates the splashing problem in the nozzle casting process, and has the advantages of simple structure, easy implementation, no influence on the normal casting process flow field, and can prevent the splashing in the nozzle casting process and the slag rolling in the normal casting process. The method can effectively reduce the splashing amount in the nozzle casting process by 10-30%. BRIEF DESCRIPTION OF DRAWINGS

[0034] The accompanying drawings, which are incorporated into and form a part of the specification, illustrate preferred embodiments of the present application and, together with the description, serve to explain the principles of the present application.

[0035] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments or the prior art description will be briefly introduced as follows. Obviously, for those skilled in the art, other drawings can also be obtained from these drawings without creative labor.

[0036] Figure 1 A flowchart of a slab casting method provided by the embodiments of the present application;

[0037] Figure 2 A structural diagram of a double-flow placeholder provided by the embodiments of the present application. DETAILED DESCRIPTION

[0038] In order to make the purpose, technical solutions and advantages of the embodiments of the present application more clear, the technical solutions in the embodiments of the present application will be described clearly and completely in combination with the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, not all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0039] Various embodiments of the present application can exist in a range of forms; it should be understood that the description in a range form is merely for the convenience and brevity, and should not be understood as a hard limitation on the scope of the present application; therefore, it should be considered that the range description has disclosed all possible sub-ranges and single values within the range. For example, it should be considered that the range description from 1 to 6 has disclosed sub-ranges, such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., as well as single values within the range, such as 1, 2, 3, 4, 5, and 6, regardless of the range. In addition, whenever a numerical range is indicated in the present application, it refers to any cited number (fraction or integer) within the indicated range.

[0040] In the present application, the orientation words such as "upper" and "lower" are specifically the directions of the drawing surface in the drawings, unless otherwise stated. In addition, in the description of the present application, the terms "include", "contain" and the like mean "include but are not limited to". In the present text, the relational terms such as "first" and "second" are merely used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between the entities or operations. In the present text, "and / or" describes the association between the associated objects, which means that there can be three relationships, for example, A and / or B can represent the cases of A alone, A and B together, and B alone. Wherein A, B can be singular or plural. In the present text, "one or more" means one or more, and "multiple" means two or more. "At least one", "at least one of the following" or the like means any combination of the items, including any combination of single or multiple items. For example, "at least one of a, b, or c", or "at least one of a, b, and c", can represent a, b, c, a-b (i.e. a and b), a-c, b-c, or a-b-c, where a, b, c can be single or multiple.

[0041] Unless otherwise specifically stated, the various raw materials, reagents, instruments and equipment used in the present application can be purchased from the market or can be prepared by existing methods.

[0042] In a first aspect, the present application provides a slab casting method, which can be seen from Figure 1 , the method comprises:

[0043] S1, placing a double-strand flow placeholder at the bottom of the submerged nozzle to obtain a nozzle with a double-strand flow placeholder;

[0044] In the embodiments of the present application, a double flow placeholder is newly added on the basis of the original submerged entry nozzle structure. In the opening pouring process, due to the low pulling speed, the submerged entry nozzle is not submerged in the molten steel, and the use of the original concave bottom nozzle will cause splashing during the rebound process after the molten steel flow hits the bottom of the nozzle. After using the method, the molten steel can be guided to flow out of the placeholder, reducing the occurrence rate of splashing. In the normal pouring process, due to the increase of the pulling speed in stages to the target pulling speed, the use of the concave bottom nozzle after the melting of the placeholder can effectively buffer the impact of high-speed flow on the meniscus fluctuation of the crystallizer, reducing the occurrence rate of slag entrapment. Therefore, the method can prevent splashing in the opening pouring process and slag entrapment in the normal pouring process.

[0045] In some embodiments, the double flow placeholder is composed of a closed triangular prism steel support with a handle, which can be seen from Figure 2 , the cross section of the double flow placeholder is an isosceles triangle; wherein,

[0046] The size parameters of the double flow placeholder are designed according to the size parameters of the submerged entry nozzle.

[0047] In some embodiments, the design of the size parameters of the double flow placeholder according to the size parameters of the submerged entry nozzle comprises:

[0048] The height of the double flow placeholder and the outlet width of the submerged entry nozzle satisfy the following relationship:

[0049] h=W-(2~4)

[0050] In the formula, h represents the height of the double flow placeholder, and W represents the outlet width of the submerged entry nozzle.

[0051] In some embodiments, the design of the size parameters of the double flow placeholder according to the size parameters of the submerged entry nozzle comprises:

[0052] The length of the base of the double flow placeholder and the inner diameter of the submerged entry nozzle satisfy the following relationship:

[0053] a=D+(2~4)

[0054] In the formula, a represents the length of the base of the double flow placeholder, and D represents the inner diameter of the submerged entry nozzle.

[0055] In some embodiments, the design of the size parameters of the double flow placeholder according to the size parameters of the submerged entry nozzle comprises:

[0056] The base angle of the double flow placeholder is equal to the inclination angle of the submerged entry nozzle.

[0057] In the embodiments of the present application, the positive effect of designing the size parameters of the double-strand flow placeholder according to the size parameters of the submerged nozzle is that the height h of the placeholder is set as W-(2-4) mm of the outlet width of the submerged nozzle, facilitating the insertion of the placeholder into the bottom of the submerged nozzle, the bottom side length a of the placeholder is D+2-4 mm, the bottom side length of the placeholder is slightly larger than the inner diameter of the submerged nozzle, so as to be fixed at the bottom of the nozzle, and the bottom angle of the placeholder is equal to the inclination angle a of the submerged nozzle. According to the trigonometric function relationship, the waist length b of the steel support can be calculated as (D+(2-4))*sin a / sin(180°-2a).

[0058] S2, baking the nozzle with the double-strand flow placeholder;

[0059] In some embodiments, the baking time is 1-2 h.

[0060] The positive effect of controlling the baking time to be 1-2 h is to prevent the cold shut after pouring molten steel due to the low temperature of the nozzle part, so as to make the inner diameter of the nozzle smaller or blocked.

[0061] S3, installing the baked nozzle with the double-strand flow placeholder at the lower part of the tundish for casting; wherein, during the casting process, the flow of argon blowing of the upper nozzle is controlled in stages.

[0062] In some embodiments, the flow of argon blowing of the upper nozzle is controlled in stages, including:

[0063] According to the relationship between the casting speed and the melting of the double-strand flow placeholder, the flow of argon blowing of the upper nozzle is controlled.

[0064] In some embodiments, the flow of argon blowing of the upper nozzle is controlled according to the relationship between the casting speed and the melting of the double-strand flow placeholder, including:

[0065] When the casting speed increases from 0 to before the melting of the placeholder, the flow of argon blowing of the upper nozzle is controlled to be 0.5-2 L / min.

[0066] In some embodiments, the flow of argon blowing of the upper nozzle is controlled according to the relationship between the casting speed and the melting of the double-strand flow placeholder, including:

[0067] When the melting of the placeholder to the casting speed is 0.8 m / min, the flow of argon blowing of the upper nozzle is controlled to be 2-4 L / min.

[0068] In some embodiments, the flow of argon blowing of the upper nozzle is controlled according to the relationship between the casting speed and the melting of the double-strand flow placeholder, including:

[0069] When the casting speed increases from 0.8 m / min to the target casting speed, the flow of argon blowing of the upper nozzle is controlled to be 3-10 L / min.

[0070] In the embodiments of the present application, the positive effect of controlling the blowing amount of the upper nozzle in stages is as follows: when the pulling rate increases from 0 to the melting of the placeholder, the liquid steel flow is not a stable stream and is easy to splash because the pulling rate is low, so the blowing amount of the upper nozzle is controlled to be small, i.e., 0.5-2 L / min. When the pulling rate increases from the melting of the placeholder to 0.8 m / min, the stability of the stream is improved to a certain extent, but the liquid steel is still easy to splash after the blowing amount is increased, so the blowing amount of the upper nozzle is controlled to be 2-4 L / min. When the pulling rate increases from 0.8 m / min to the target pulling rate, the liquid steel flows over the submerged nozzle, and in order to prevent the nozzle from being blocked, a certain amount of argon blowing is needed, so the argon blowing flow is controlled to be 3-10 L / min.

[0071] The method of the present application is suitable for casting slabs with a width of 900-2000 mm and a thickness of 150-400 mm.

[0072] The present application will be further described below in combination with specific examples. It should be understood that these examples are only used to illustrate the present application and are not used to limit the scope of the present application. The experimental methods in the following examples are not specified, and the methods are generally determined according to national standards. If there is no corresponding national standard, the methods are determined according to the general international standards, conventional conditions, or the conditions suggested by the manufacturers.

[0073] Example 1

[0074] A double-stream placeholder is placed at the bottom of the submerged nozzle to obtain a nozzle with a double-stream placeholder, and the nozzle is baked for 1.5 h after baking. After baking, the nozzle with the double-stream placeholder is installed at the lower part of the tundish for casting. The nozzle is used to cast IF steel, the casting slab has a width of 1400 mm, a thickness of 237 mm, a target pulling rate of 1.4 m / min, a nozzle outlet width W = 70 mm, a submerged nozzle inner diameter D = 78 mm, and a nozzle downward inclination angle of 15°. The blowing amount of the upper nozzle is controlled to be 1.1 L / min when the pulling rate increases to the melting of the placeholder. The blowing amount of the upper nozzle is controlled to be 2.3 L / min when the placeholder is melted and the pulling rate increases to 0.8 m / min, and the argon blowing flow is controlled to be 4.5 L / min when the pulling rate increases from 0.8 m / min to the target pulling rate. The placeholder is composed of a closed triangular prism steel support with a handle, the height of the steel support h = 68 mm; the cross section of the placeholder is an isosceles triangle, the bottom side length a = 80 mm, the bottom angle is equal to the nozzle downward inclination angle of 15°, and the waist length b = 80*sin15° / sin150° = 41.4 mm. The method of the present application can effectively reduce the spatter amount by 12% during the casting start-up process.

[0075] Example 2

[0076] A double strand flow placeholder is placed at the bottom of the submerged entry nozzle to obtain a nozzle with double strand flow placeholder, and then baked for 1.8 hours. After baking, the nozzle with double strand flow placeholder is installed at the lower part of the tundish for casting. The nozzle is used to cast LCAK steel, with a casting billet width of 1100 mm, a casting billet thickness of 237 mm, and a target pulling speed of 1.8 m / min. The nozzle outlet width W is 70 mm, the submerged entry nozzle inner diameter D is 78 mm, and the nozzle downward inclination angle is 20°. The pulling speed is increased to before the placeholder melts, and the upper nozzle gas blowing amount is controlled at 1.4 L / min. The placeholder melts to the pulling speed is increased to 0.8 m / min, the upper nozzle gas blowing amount is controlled at 2.5 L / min, the pulling speed is increased from 0.8 m / min to the target pulling speed, and the argon blowing flow rate is controlled at 3.6 L / min. The placeholder is composed of a closed triangular prism steel support with a handle, the height of the steel support h is 67 mm; the placeholder cross section is an isosceles triangle, the bottom side length a is 80 mm, the bottom angle is equal to the nozzle downward inclination angle 20°, and the waist length b is 42.5 mm. After the method of the application is used, the spatter amount during the start casting process can be effectively reduced by 14%.

[0077] Example 3

[0078] A double strand flow placeholder is placed at the bottom of the submerged entry nozzle to obtain a nozzle with double strand flow placeholder, and then baked for 1.6 hours. After baking, the nozzle with double strand flow placeholder is installed at the lower part of the tundish for casting. The nozzle is used to cast IF steel, with a casting billet width of 1200 mm, a casting billet thickness of 230 mm, a target pulling speed of 1.6 m / min, a nozzle outlet width W of 60 mm, a submerged entry nozzle inner diameter D of 72 mm, and a nozzle downward inclination angle of 15°. The pulling speed is increased to before the placeholder melts, and the upper nozzle gas blowing amount is controlled at 1.4 L / min. The placeholder melts to the pulling speed is increased to 0.8 m / min, the upper nozzle gas blowing amount is controlled at 2.5 L / min, the pulling speed is increased from 0.8 m / min to the target pulling speed, and the argon blowing flow rate is controlled at 3.6 L / min. The placeholder is composed of a closed triangular prism steel support with a handle, the height of the steel support h is 67 mm; the placeholder cross section is an isosceles triangle, the bottom side length a is 75 mm, the bottom angle is equal to the nozzle downward inclination angle 15°, and the waist length b is 38.8 mm. After the method of the application is used, the spatter amount during the start casting process can be effectively reduced by 16%.

[0079] Example 4

[0080] A double strand flow placeholder is placed at the bottom of the submerged nozzle to obtain a nozzle with double strand flow placeholder, and post baking is performed for 1.3 hours; after baking, the nozzle with double strand flow placeholder is installed at the lower part of the tundish for casting. The LCAK steel is cast using the nozzle, the slab width is 1200 mm, the slab thickness is 230 mm, the target casting speed is 1.5 m / min, the nozzle outlet width W=60 mm, the submerged nozzle inner diameter D=72 mm, and the nozzle downward inclination angle is 20°. When the casting speed is increased to before the placeholder is melted, the upper nozzle argon blowing amount is controlled to be 1.7 L / min. When the placeholder is melted, the casting speed is increased to 0.8 m / min, the upper nozzle argon blowing amount is controlled to be 2.1 L / min, the casting speed is increased from 0.8 m / min to the target casting speed, and the argon blowing amount is controlled to be 5.6 L / min. The placeholder is composed of a closed triangular prism steel support with a handle, the height of the steel support h=67 mm; the cross section of the placeholder is an isosceles triangle, the bottom side length a=74 mm, the bottom angle is equal to the nozzle downward inclination angle 20°, and the waist length of the steel support b=74*sin20° / sin140°=39.4 mm. After the method of the present application is used, the spatter amount during the start-up casting process can be effectively reduced by 17%.

[0081] The above description is merely that of a specific implementation of the present application, and persons skilled in the art can understand or implement the present application based on the above description. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to the embodiments shown herein, but will conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for casting slabs, characterized in that, The method includes: The dual-flow sump is placed at the bottom of the submersible nozzle to obtain a nozzle with a dual-flow sump. The sprue with the dual-flow spacer is baked. The baked sprue with dual-flow occupier is installed at the bottom of the tundish for casting; wherein, during the casting process, the flow rate of argon gas blowing from the upper sprue is controlled in stages; The dual-flow stencil is composed of a closed triangular prism steel bracket with a handle, and the cross-section of the dual-flow stencil is an isosceles triangle; the base angle of the dual-flow stencil is equal to the inclination angle of the submersible nozzle; The phased control of the argon gas flow rate at the upper water inlet includes: Before the casting machine speed is increased from 0 to the point where the spacer melts, the air blowing rate at the top nozzle is controlled to be 0.5-2 L / min. The spacer is melted to the casting machine speed of 0.8 m / min, and the air blowing volume at the top of the sprue is controlled to be 2-4 L / min; Increase the casting speed from 0.8 m / min to the target casting speed, and control the air blowing volume at the top nozzle to 3-10 L / min.

2. The method according to claim 1, characterized in that, The dimensions of the dual-flow occupant are designed based on the dimensions of the immersion nozzle.

3. The method according to claim 2, characterized in that, The step of designing the dimensional parameters of the dual-flow occupant based on the dimensional parameters of the immersion nozzle includes: The height of the dual-flow occupant and the outlet width of the submersible nozzle satisfy the following relationship: h = W - (2~4) In the formula, h represents the height of the dual-flow occupier, and W represents the outlet width of the immersion nozzle.

4. The method according to claim 2, characterized in that, The step of designing the dimensional parameters of the dual-flow occupant based on the dimensional parameters of the immersion nozzle includes: The bottom side length of the dual-flow occupant and the inner diameter of the submersible nozzle satisfy the following relationship: a = D + (2~4) In the formula, a represents the bottom side length of the dual-flow occupier, and D represents the inner diameter of the immersion nozzle.

5. The method according to claim 1, characterized in that, The baking time is 1-2 hours.

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